The present disclosure relates to techniques to reduce noise included in image signals.
Japanese Patent Publication No. 2000-106630 discloses a technique to reduce noise included in image signals by using two-dimensional digital noise reduction (DNR). According to this technique, whether or not there is a correlation between a target pixel whose noise will be reduced and each of pixels adjacent to the target pixel is determined, and pixel values of the adjacent pixels determined to be correlated with the target pixel are added up and averaged, thereby obtaining a pixel value. Then, the target pixel is replaced with a pixel corresponding to the obtained pixel value. Thus, the larger the number of adjacent pixels determined to be correlated with the target pixel is, the more noise reduction effect can be enhanced.